A satisfactory dentifrice composition should have a cosmetic effect upon the teeth, namely, keeping them light colored. It should also dean and remove debris as well, thereby aiding the prevention of tooth decay and promoting gingival health. Abrasives aid in the removal of the tightly adherent pellicle film. This film usually comprises a thin acellular, glycoprotein-mucoprotein coating which adheres to the enamel within minutes after teeth are cleaned. The presence of various food pigments lodged within the film accounts for most instances of teeth discoloration. Ideally, an abrasive should provide satisfactory removal (cleaning) of the pellicle film with minimal damage (abrasion) to oral tissue, i.e. the dentin and enamel.
Beyond the pellicle cleaning aspect, incorporating an antiplaque agent(s) provides additional benefits. The formation of dental plaque is the primary source of dental caries, gingival and periodontal disease, and tooth loss. Plaque is a mixed matrix of bacteria, epithelial cells, leukocytes, macrophages and other oral exudate The bacteria associated with plaque can secrete enzymes and endotoxins which can irritate the gums and cause an inflammatory gingivitis. As the gums become increasingly irritated by this process, they have a tendency to bleed, lose their toughness and resiliency, and separate from the teeth. This separation results in periodontal pockets leading in turn to further accumulation of debris, secretions, and more bacteria/toxins. This process eventually leads to destruction of both the hard and soft tissue of the oral cavity.
The use of a variety of agents to clean the oral cavity and reduce plaque and mouth malodor has been recognized for some time. Examples include: U.S. Pat. No. 3,696,191, Oct. 3, 1972 to Weeks; U.S. Pat. No. 3,991,177, Nov. 9, 1976 to Vidra et al.; U.S. Pat. No. 4,058,595, Nov. 15, 1977 to Colodney; U.S. Pat. No. 4,115,546, to Vidra et al.; U.S. Pat. No. 4,133,476, Feb. 6, 1979 to Simonson et al.; U.S. Pat. No. 4,140,758, Feb. 20, 1979 to Vidra et al.; U.S. Pat. No. 4,154,815, May 15, 1979 to Pader; U.S. Pat. No. 4,737,359, Apr. 12, 1983 to Eigen et al.; U.S. Pat. No. 4,936,981, Jan. 22, 1991 to Glace et al.; U.S. Pat. No. 4,992,420, Feb. 12, 1991 to Nesser; U.S. Pat. No. 5,000,939, Mar. 19, 1991 to Dring et al.; Kokai 02/105,398, published Apr. 13, 1990 to Kao Corporation; Kokai 03/128,313, published May 31, 1991 to Nippon Kotai Kenkyu and Kokai 03/223,209, published Oct. 2, 1991 to Lion Corporation; U.S. Pat. No. 4,652,444, Mar. 24, 1987 to Maurer; U.S. Pat. No. 4,725,428, Feb. 16, 1988 to Miyahara et al.; U.S. Pat. No. 4,355,022, Oct. 19, 1982 to Rabussay and PCT application WO 86/02831, published May 22, 1986 to Zetachron, Inc.
Abrasives are described in U.S. Pat. No. 4,340,583, Jul. 20, 1982 to Wason, U.S. Pat. No. 3,574,823, Apr. 13, 1971 to Roberts et al., EP Patent 535,943A1, Apr. 7, 1993, McKeown et al., and PCT Patent WO 92/02454, Feb. 20, 1992 to McKeown et al.
Moreover, various combinations of silicas have been described in the art. Silica combinations involving compositions of differing particle sizes and specific surface areas are disclosed in U.S. Pat. No. 3,577,521 to Karlheinz Scheller et al., May 4, 1971 and U.S. Pat. No. 4,618,488 to Macyama et al., Oct. 21, 1986, respectively. Similarly, U.S. Pat. No. 5,110,574 to Reinhardt et al., May 5, 1992 discloses combining precipitated thickener and polishing silicas to form silica compositions having oil absorption values of at least 200. Further examples of silica combinations include U.S. Pat. No. 5,124,143 to Muhlemann, Jun. 23, 1992 and U.S. Pat. No. 4,632,826 to Ploger et al., Dec. 30, 1986.
While the prior art discloses a variety of silica compositions useful as dental cleaning abrasives, there is still a need for additional compositions providing improved cleaning with minimal abrasion. The present inventor has discovered amorphous silica abrasive compositions comprising precipitated and gel silicas providing improved dental cleaning with minimal abrasion.
Accordingly, it is the object of the present invention to provide a precipitated silica and gel silica compositions providing improved pellicle cleaning without a corresponding increase in dentin or enamel abrasion. Another object of the present invention is to provide an improved method for the prevention or removal tooth stains. A further object of the present invention is to provide an improved method for the prevention or removal of plaque. These and other objects will become readily apparent from the disclosure which follows.